Go Concepts - Functions

External

• Function type specification https://golang.org/ref/spec#Function_types

Internal

• Go Concepts

Function Definition

A function declaration starts with the func keyword and it consists in a series of statements applied on a number of inputs, resulting in a number of outputs. Same inputs will always result in the same outputs. Function do not depend on a type instance's state. From this perspective, functions are conceptually different from methods.

Syntax

func <name>(
    [parameter-identifier1] [type1], [parameter-identifier2] [type2], ...) [(
    <return-type1>, [return-type2], ...)] {

   // function's body
   statement1
   statement2
   ...

   return <return-value1>, <return-value2>
}

The return type declarations are optional, if the function does not return anything.

A function may return one or more results.

Examples:

func add(a int, b int) (int) {
   return a + b;
}

The main() Function

Compiling an Executable

Built-in Functions

The built-in functions are available by default, without the need to import any package. They are what the specification calls pre-defined function identifiers. Their semantics depends on the arguments.

make()	append()	copy()	delete()	.
new()	len()	cap()	.	.
.	.	.	.	.

Closures

Anonymous function that capture local variables.

More about closures is available here.

Methods

A method defines the behavior of a type, and it relies on the state of an instance of the type. The method will - and it is supposed to - change the state. From this point of view, the method is conceptually different from a function.

A method is always exported by the package it is enclosed in.

Syntax

func <receiver> <method-name> (...) {

    // the rest of declaration is similar to a function's
    ...
}